Based on our record, Google Design Sprint Kit seems to be more popular. It has been mentiond 1 time since March 2021. We are tracking product recommendations and mentions on various public social media platforms and blogs. They can help you identify which product is more popular and what people think of it.
Also Google (as in the company not the verb) has a free version of their discovery techniques here https://designsprintkit.withgoogle.com/. Source: about 1 year ago
FlowMapp - FlowMapp is a UX planning tool for creating visual sitemaps and user flow.
Sprint - How to solve big problems and test new ideas in 5 days
StdLib - Discover pre-built APIs, compose your own and build apps
Design Principles - An open source repository of design principles and methods
Craftwork - A collection of User Interface resources made by Craftwork
Land Book - The homeland for fine websites